Matt Bissonnette, one of the SEAL Team Six operators on the raid, partially outs the reason in his book, No Easy Day. The book reads, “In his death throes, he was still twitching and convulsing. Another assaulter and I trained our lasers on his chest and fired several rounds. The bullets tore into him, slamming his body into the floor until he was motionless” (No Easy Day, Chapter 15). But this is perhaps the most measured and polite description that one could give of how operator after operator took turns dumping magazines-worth of ammunition into Bin Laden’s body, two confidential sources within the community have told us. When all was said and done, UBL had over a hundred bullets in him, by the most conservative estimate. http://sofrep.com/33599/why-us-govt-hasnt-released-photos-ubl-corpse/ I don't see why it would matter? Unless the shots left him unrecognizable.